Some gaze upward, where the morning sun streams into the chapel and spreads oval patterns of circular window panes on the white plaster wall and the pine panelling below, where the muted audience sits in a meditative trance.

The listeners are, in their own private imaginations, moved back in time, to the 18th century when listening to an organist play was an uncommon experience.

And they are hearing the music of that time - a sprightly march commissioned to celebrate a martial victory, a tune by Antonio Vivaldi, a voluntary by George Frideric Handel, a minuet by Peter Pelham - exactly as it was heard in colonial America.

And it is being played this Saturday morning on an antique tracker organ by Jock Darling in the chapel of the Wren Building on the William and Mary campus.

"No where else in the United States today can you hear an authentic 18th-century organ in an 18th-century setting," Darling has explained to the tourists who have randomly filled the hall. "This is the same sound that Thomas Jefferson and George Washington and all those fellows heard. This organ is not a reproduction; it is the real thing."

The visitors, out-of-town tourists mostly, are delighted to have wandered upon this unexpected opportunity to pause in their busy rounds of traipsing through Williamsburg for a few peaceful moments of reflection.

"This organ," Darling says proudly and somewhat possessively, "is one of the oldest in the country today and is typical of the small English organs that would be found in some of the principal churches in the larger colonial cities. There were perhaps half a dozen in all of Virginia.

"It is a tracker organ and has 302 pipes. By tracker, it is meant that the mechanical action is made entirely of wood, from the windchest to the pipes. And there are no foot pedals.

"The only change that has been made has been the addition of an electric pumper to fill the air bellows."

But this is not an organ that was in Williamsburg in the 18th century. It is an organ that was purchased by The Colonial Williamsburg Foundation and brought in 1953 from the Kimberly Hall, a country estate in Norfolk, England, to be placed in the Supper Room of the reconstructed Governor's Palace.

"But it was too large for that room," Darling explained, "and it was moved to the reception hallway of the Williamsburg Conference Center, where it stood - virtually unplayed - until 1971 when it was moved to the balcony of the Wren Chapel."

And every Saturday morning since September 1971, Darling has "sat on the bench" - or has arranged for JanEl Gortmaker or Michael Monaco or some other substitute - and presented a half-hour recital for anyone who wishes to come. During this Christmas season, recitals in the Wren Chapel have been scheduled more frequently - at 11 a.m. daily, beginning Dec. 18, except Sundays and Christmas and New Year's Day.

James S. Darling III, who will be 70 come May, is the organist and choirmaster of Bruton Parish Church - and has been since the summer of 1961. And as a harpischordist and scholar of note, he has been an adviser to and a performer for Colonial Williamsburg. And he is an adjunct member of the music faculty at W&M, where he tutors organ students. He has written of and compiled a book of the music Thomas Jefferson played; he has dedicated new organs in churches around the state; he has made recordings; he has performed for scores of visiting dignitaries - including four presidents, foreign heads of state, "and the Chinese Ping-Pong team."

He has been called - perhaps a little to his chagrin - the modern-day Peter Pelham of Williamsburg. In the 18th century, Pelham was the city's jailer and the organist at Bruton. He composed some music - music that Darling keeps alive today.

Darling, however, is not a composer, but a talented pianist and organist and teacher. He grew up in Hampton, in his grandmother's mansion, Cedar Hall. That massive landmark on the point where Sunset Creek joins the Hampton River has long been gone, but descendants of James Sands Darling, an entrepreneur who came from New York just after the Civil War, still live in Hampton.

"Jock was the oldest, and we lived with our grandmother, Mrs. Frank W. Darling - Molly Darling, who was well known and even today well remembered," recalls Jock Darling's sister, Ann Darling Tormey of Hampton. Her recollections of childhood at Cedar Hall include that of Jock playing bridge, at the age of 8, with Molly Darling and her friends, and of his playing the piano. "Grandmother liked music, and when people were invited to Cedar Hall - there was singing, and Jock played.

"And he wouldn't just play," she continued. "He would stand by the keyboard and talk about the music - just as he does so often today."